The invention relates to an orthopedic retaining system comprising at least one bone screw which has a head part and a threaded shaft pivotally mounted on it, a clamping element which is mounted in the head part, can be pressed against the threaded shaft from the upper side of the head part and, as a result, secures the threaded shaft relative to the head part, a retaining bar which is arranged in a receptacle of the head part and extends essentially transversely to the threaded shaft and a clamping device on the upper side of the head part, by means of which the clamping element and the retaining bar are pressed into the head part in such a manner that the threaded shaft and the retaining bar are secured in position relative to the head part.
Orthopedic retaining systems of this type are used to fix bones and bone fragments in position relative to one another; for this purpose, bone screws are screwed into the bones and bone fragments and then connected to one another by means of the retaining bar such that the orthopedic retaining system comprising the bone screws and the retaining bar forms as such a rigid member which fixes the bones and bone fragments relative to one another in their position. In this respect, it is known to design the head part and the threaded shaft of the clamping screw so as to be pivotable relative to one another, either pivotable in all directions as a result of a ball connection or pivotable about an axis extending transversely to the longitudinal axis of the threaded shaft as a result of a limited mounting. When the orthopedic retaining system is used, it is, therefore, possible to pivot the head part in relation to the threaded shaft and, in addition, displace the retaining bar in relation to the head part; these degrees of freedom are restricted only when the clamping device is actuated, i.e., the pivotability is eliminated when the clamping device is actuated and the free displaceability of the retaining bar. In the case of known devices (DE 10 2005 021 879 A1), this is brought about, for example, by screwing a clamping screw into the head part, this screw being supported on the retaining bar which then rests, for its part, on the clamping element. In this way, the displaceability of the retaining bar and the pivotability of the threaded shaft in relation to the head part are, in any case, terminated at the same time when the clamping device is actuated.
This can be disadvantageous since, for the purpose of aligning the orthopedic retaining system in these arrangements, either the retaining bar is freely displaceable and also the threaded shaft pivotable or, however, both possibilities for movement are blocked.
The object of the invention is to design an orthopedic retaining system in such a manner that the operator has the possibility, with the simplest of means, of curtailing some elements of the movability of head part, retaining bar and threaded shaft whilst still retaining other elements of the movability.